1. Field of the Invention
The invention relates to a method and arrangement for prediction and regulating a paper winding characteristic variable in a paper winding device to achieve a constant reeling layer thickness (improved quality) in the production process that controls the line force or the web tension.
2. Description of the Related Art
During the manufacture of paper, the paper is wound up, in webs up to 10 meters wide, onto a parent reel for intermediate storage and further processing. The diameter of the parent reel may be up to 3 meters or more. During further processing, this paper web runs through a slitter to be tailored to customer-specific specifications, and is cut into paper web widths of different width on the slitter and wound up onto cores which can be supplied to customers.
Paper-specific problems can occur in the production of these customer reels. The paper is reeled up onto the parent reel under tensile stress in the horizontal direction, and by pressing it in the radial direction of the sleeve. This reeling process introduces viscoelastic effects of the paper. The reeling-up mechanism impresses a wide variety of properties onto the paper, since the forces used in the process are stored in the layers of the parent reel.
As the paper is unwound from the parent reel onto another reel, it is again subjected to tangential and radial forces. The aim during this winding operation is to reel up the paper reel produced with an optimum winding hardness so that, in particular, no telescoping of the paper reel occurs, nor does any plastic deformation of the paper within the reel occur. Since the material characteristics of the wound paper vary from grade to grade, this is a very complex problem.
The reel hardness or the winding hardness is normally used as a measure for assessing the quality of the reel produced. For this paper winding characteristic variable there exist different definitions, of which one, for example, is the average layer thickness: during the reeling-up operation, the number of layers wound and the increase in radius are determined. In this way, the average layer thickness is obtained, which is normally averaged over 100 layers. In order to be able to compare the average layer thickness between individual paper grades better, this variable is related to the paper thickness in the unstressed state of the respective grade which gives a characteristic number that is generally less than 1. The lower it is, the harder the reel has been wound (i.e., it has a high winding hardness). In the other case, the average normalized layer thickness is relatively high, which corresponds to a low winding hardness. These variables are normally plotted against the diameter as illustrated, for example, in FIG. 2. Depending on whether reeling up or unwinding is concerned, one may speak of reeling or unwinding curves or else of reeling layer thickness curves. The course of such a curve provides information about the quality of the reel produced. It generally exhibits sharp fluctuations, which make an interpretation in relation to the quality considerably more difficult. In practice, a reel is designated as optimally wound if the reeling curve has a virtually constant course, with the exception of the start and end of the winding operation. The mean value of the curve is used for assessment.
In a manner similar to the reel winding hardness, a reel unwinding hardness in relation to the parent reel is defined. It can be seen from the curves in FIG. 2 that the reel winding curve (AU) and the reel unwinding curve (AB) influence each other. Furthermore, it can be seen that despite the force relationships being regulated to be constant during the winding operation, the course of the reeling curve follows the unwinding curve of the parent reel. However, as outlined at the beginning, such a behavior of the paper reel during the reeling-up operation is not desired.
The problem on which the invention is based is therefore to specify a method and an arrangement with which a paper winding characteristic variable which is critical during the paper winding operation can be predicted and/or regulated.
This object is achieved by a method of predicting a paper winding characteristic variable in a paper winding device, comprising the steps of:
a) unwinding paper from a first paper reel and winding the paper onto a second paper reel;
b) determining, in a preparatory step, depending on a measurable time-dependent characteristic variable of the step of winding at a known first influencing force at least the first paper winding characteristic variable of the first paper reel and a second paper winding characteristic variable of the second paper reel, the first paper winding characteristic variable and the second paper winding characteristic variable being results of the preparatory step;
c) setting a predictor that predicts a future second paper winding characteristic variable, utilizing the results of the preparatory step which are a function of the first and the second paper winding characteristic variable, and a time variable
This object is also achieved by a method of regulating a paper winding characteristic variable in a paper winding device via influencing forces which influence the paper winding characteristic variable, comprising the steps of:
a) unwinding paper from a first paper reel and winding the paper onto a second paper reel under the influence of one of the influencing forces;
b) determining, in a first preparatory step, depending on at least one measurable time-dependent characteristic variable of the step of winding at a constant first influencing force, a first paper winding characteristic variable of the first paper reel and a second paper winding characteristic variable of the second paper reel, the first paper winding characteristic variable and the second paper winding characteristic variable at the first influencing force being results of the first preparatory step;
c) determining, in a second preparatory step, depending on at least the measurable characteristic variable of the step of winding at a known second influencing force, a second paper winding characteristic variable and a time duration for this determination operation, as a determination time, the second paper winding characteristic variable and the time duration at the second influencing force being results of the second preparatory step;
d) setting a predictor that predicts a future second paper winding characteristic variable, utilizing the results from the first preparatory step, as a function of the second paper winding characteristic variable, and a time variable;
e) setting a controller that regulates, as a function of the second paper winding characteristic variable provided to it, an influencing force associated with the second paper winding characteristic variable, utilizing the results of the first preparatory step and the second preparatory step;
f) providing the controller, during a control operation, a desired second paper winding characteristic variable,
using the second paper winding characteristic variable on the paper winding device as an actual paper winding characteristic variable,
determining a predicted paper winding characteristic variable using a determination time and the actual paper winding characteristic variable, and
regulating an influencing force of the control operation by providing a control difference which is formed with the predicted paper winding characteristic variable being used together with the desired second paper winding characteristic variable.
This object is also achieved by an arrangement for predicting a paper winding characteristic variable in a paper winding device, comprising:
a) a first and a second paper reel, paper being unwound from the first paper reel and wound up onto the second paper reel;
b) a predictor which has been set to predict a future second paper winding characteristic variable using results from a preparatory step, the preparatory step determining, depending on a measurable time-dependent characteristic variable of paper being wound up onto the second paper reel, a first paper winding characteristic variable of the first paper reel and a second paper winding characteristic variable of the second paper and a time variable;
c) a determining mechanism for determining the paper winding characteristic variable from the measurable time-dependent characteristic variable; and
d) a measuring device for measuring the paper winding characteristic variable.
Finally, this object is achieved by an arrangement for regulating a paper winding characteristic variable in a paper winding device via an influencing force which influences the paper winding characteristic variable, comprising:
a first and at least a second paper reel, paper being unwound from the first paper reel and wound up onto the second paper reel, which constitute a winding operation, under the influence of the influencing force;
a predictor which has been set to predict a future second paper winding characteristic variable using results from a first preparatory step,
the first preparatory step determining, depending on at least one measurable time-dependent characteristic variable of the winding operation at a known first influencing force at least a first paper winding characteristic variable of the first paper reel and a second paper winding characteristic variable of the second paper reel and a determination time;
a determining mechanism for determining the paper winding characteristic variable from the measurable time-dependent characteristic variable within the determination time;
a measuring device for measuring the paper winding characteristic variable;
a controller which has been set using results from the first and the second preparatory steps,
the preparatory steps determining, depending on at least the measurable time-dependent characteristic variable of the winding operation at a known second influencing force, at least the second paper winding characteristic variable and a time duration for a determination operation as the determination time,
the controller regulating, as a function of the paper winding characteristic variable fed to it, an influencing force associated with the paper winding characteristic variable,
predefining a desired second paper winding characteristic variable during a regulation operation,
determining the second paper winding characteristic variable on the paper winding device by the determining mechanism as an actual paper winding characteristic variable, and
the predictor predicting the paper winding characteristic variable with the determination time, and the the actual paper winding characteristic variable as the predicted paper winding characteristic variable which is used, together with the desired second paper winding characteristic variable, to form a control difference which is fed to the controller to regulate the influencing force.
Advantageously, when different paper reels are being unwound and wound, the behavior of the paper and of the associated paper winding characteristic variables is similar. Use may be made of this fact in order to train a predictor or to impress this behavior on it, in order to be able to predict the behavior of the paper winding characteristic variable for future winding operations.
Advantageously, the result of the prediction of the paper winding characteristic variable can be used to influence the forces, which are normally kept constant in paper winding devices, in accordance with the desired paper winding characteristic variable, by the behavior of the paper winding characteristic variable. This behavior depends on the influencing force, which is impressed on a controller and this controller being fed with a control difference formed from the desired winding characteristic variable and the predicted actual paper winding characteristic variable. The controller uses these variables to determine a compensation force, which is superimposed on an influencing force which is critical during the winding operation.
Advantageously, the method and the arrangement can also be employed when the paper is being wound from a larger reel onto smaller reels and, at the same time, the paper is being slit into webs.
Advantageously, for the case in which a wide paper web is being slit and wound up onto narrower paper reels, the result of the various predicted actual paper winding characteristic variables can be superimposed to form a common variable, in order to drive the controller.
Advantageously, when the proposed method is used, or the proposed arrangements are employed, simple measured variables, such as the radius of the paper or the angular velocity of the different paper reels, are registered in order to predict the actual paper winding characteristic variable or to determine the layer thickness from these variables.
Particularly advantageously, the proposed methods and arrangements can be employed both for regulating the line force and for regulating the web tension as the influencing force.
Advantageously, neural networks can be used as the predictor and PID controllers as the controller, since there is sufficient experience with these devices and no great expenditure is required for training or adapting these devices to specific problems during paper winding.
Advantageously, the proposed arrangements can be used in paper-reel slitters, since these have high quality requirements and an improvement can be achieved by way of the proposed methods.
Advantageously, the proposed method and the proposed arrangement can also be used in paper-like materials which have similar mechanical characteristics (i.e., a viscoelastic behavior and an elastic/plastic deformation like paper).